Présentations Colloques

Oral Presentation
Session 8.04: Isotopic and residence time tracers
Arnoux Marie
Lakes as groundwater window inferred from isotope signal, insight for sustainable management
At a global scale, lakes are under severe pressure due to an increasing anthropogenic impact from a growing population in a more developed world. Accordingly, many lakes show today a decrease of water quality. Recent studies have highlighted that global warming and subsequent change in water use will further enhance the eutrophication process in lakes. Groundwater influences lakes ecosystems but also lakes sensitivity to climate and environmental changes and therefore their resilience. However, interactions between lakes and groundwater are not well known and, most of the time, they are not considered in lakes budgets. These interactions should be thus precisely quantified for lake restoration and insight in sustainable lake management in the future. In our study, a groundwater-connected lake with a small catchment was chosen to quantify variations of groundwater-lake fluxes over time and their related influences on the lake’s water geochemistry. Variations of geochemical tracers, i.e. water stable isotopes and radon-222, linked to groundwater inflows are determined through their analyses in space and time and a precise instrumentation of the lake. Results of this study at short time scale are then combined with a regional study at seasonal time scale to determine the sensitivity of small lakes to changes in groundwater in a cold continental climate. The groundwater inflows to lakes are quantified in terms of flux percentages and allow the discussion of lake evolution in a climate and environmental changes perspective.